1. Field of the Invention
The present invention relates to a film forming unit for a substrate.
2. Description of the Related Art
In a photolithography process in semiconductor device fabrication processes, for example, resist coating treatment in which a resist solution is applied to the top surface of a wafer to form a resist film, exposure processing in which the wafer is exposed in a pattern, developing treatment in which development is performed for the exposed wafer, and the like are performed to form a predetermined circuit pattern on the wafer. Such a photolithography process is performed in a coating and developing unit. The coating and developing unit has a resist coating unit which performs resist coating treatment.
In a conventional resist coating unit, a spin coating method is in the mainstream as a method of applying a resist solution. According to the spin coating method, the resist solution is discharged to the center of a wafer and the wafer is rotated. This allows the resist solution applied on the wafer to spread by centrifugal force, whereby a uniform resist film can be formed over the entire surface of the wafer.
However, in the spin coating method, since the wafer is rotated at high speed, a large amount of the resist solution scatters from the peripheral portion of the wafer, resulting in a big waste of the resist solution. Further, the apparatus is contaminated by the scatter of the resist solution, which causes harmful effects such as a need to clean it frequently.
Hence, in place of the spin coating method, the inventors consider an apparatus in which a discharge nozzle for discharging a resist solution and a wafer move relative to each other to apply the resist solution. This newly conceived coating unit has a linear slide means for moving the discharge nozzle back and forth above the wafer, wherein the linear slide means has a slider slidably attached to a guide shaft, and to the slider the discharge nozzle is attached. Therefore, the discharge nozzle can apply the resist solution linearly on the wafer when it moves along the guide shaft. Meanwhile the wafer which is supported horizontally is moved by another drive mechanism in a direction perpendicular to the direction in which the discharge nozzle slides.
The discharge nozzle discharges the resist solution to the wafer W while moving back and forth. Meanwhile, the wafer moves intermittently in a direction perpendicular to the direction in which the discharge nozzle slides. By such complex movements, the discharge nozzle scans over the wafer, and as a result, the resist solution is applied sequentially in the manner of the so-called continuous stroke. In this case, the discharge nozzle moves at highest speed when it moves above the wafer, decreases its speed to return when it comes to be above the peripheral portion of the wafer, accelerates to move at high speed after that, and moves over the wafer again.
In the resist coating unit in which the resist solution is applied in the manner of the so-called continuous stroke, it is necessary to move the discharge nozzle at as high speed as possible so that it can perform a quick resist coating. However, if the slider is attached to a guide rail by means of a bearing such as a ball bearing, slide resistance is caused. In such a case, if the discharge nozzle moves at high speed, vibration due to the slide resistance occurs, so that the discharge nozzle is made to move slightly, which may prevent the precise linear resist coating from being performed. Furthermore, it is feared that this vibration may be transferred to other units provided at the coating and developing unit, whereby giving bad effects on the processes in other units. Moreover, a fear is brought about that the decrease and increase in the speed of the discharge nozzle when it makes a turn may not be carried out smoothly due to the slide resistance, and may require a longer time. Therefore, there is room for improvement regarding these points to realize the resist coating of high precision.
The present invention is made in consideration of the above points and its first object is to reduce slide resistance to restrain the aforesaid vibration when the discharge nozzle is moved.
Furthermore, in the aforesaid coating method in the continuous stroke manner, since the coating is performed on the entire surface of the linearly coating areas by placing them side by side, the discharge nozzle has to scan them many times, and therefore it is practical to shorten the processing time by maximizing the scanning speed of the nozzle.
Hence, it is considered to increase the speed of the nozzle, which is moving, for example, at 6 m/s to 10 m/s, by several m/s at one end, and decrease it sharply at the other end when the nozzle moves in an X-direction, but there is a problem that a big vibration occurs at the time of the increase and decrease in speed of the nozzle. Therefore, if the scanning speed of the nozzle is tried to be increased to raise a throughput, the vibration increases, thus causing a fear that the vibration may be transferred, for example, to the other units in the coating and developing system and even to the aligner.
The present invention is made in consideration of the above circumstances, and its second object is to provide a coating film forming unit which can form a coating film with higher yields and a uniform quality, and which performs a higher throughput as well. Yet another object of the present invention is to provide a coating film forming unit with less vibration.
In order to attain the aforesaid first object, according to a first aspect of the present invention, a film forming unit of the present invention is a film forming unit for supplying a coating solution onto a substrate from a discharge nozzle to form a film on the substrate, including moving means for moving the discharge nozzle, and the aforesaid moving means includes a support member for supporting the discharge nozzle, a moving member for moving the aforesaid support member, a guide shaft passing through bearing portion formed in the aforesaid supporting member, and a gas supplying part for supplying gas into a space between the aforesaid bearing portion and the aforesaid guide shaft.
According to the present invention, the moving means moves the discharge nozzle via the supporting member. The discharge nozzle discharges the coating solution while moving along the guide shaft. The coating solution is applied along the locus of the movement of the discharge nozzle on the substrate. Since gas is supplied from the gas supply mechanism into a gap between the bearing portion and the guide shaft, the supporting member can float in the air relative to the guide shaft. Accordingly, the bearing portion and the guide shaft are not in mechanical contact, thus hardly causing slide resistance. As the result, even if the discharge nozzle is moved at a high speed, vibration caused by the slide resistance can be reduced, and the very small movement of the discharge nozzle does not cause disturbance in the discharge of the coating solution, thus a predetermined coating solution is accurately applied. Further, the situation in which vibration is transmitted to the other units to have adverse effects on the process of the other units can be prevented.
According to a second aspect of the present invention, the aforesaid moving means further includes a moving mechanism, and has a cover for covering the aforesaid moving mechanism, and exhaust ports formed in the aforesaid cover for exhausting atmosphere inside the aforesaid cover.
According to the above configuration, even if particles such as dust occur due to the operation of the moving mechanism, the moving mechanism is covered with the cover and the atmosphere inside the cover is exhausted from the exhaust port, therefore making it possible to exhaust the particles out of the cover without scattering them around. As the result, the situation in which the scattered particles attach onto the substrate can be prevented, and yield is enhanced. Even if the components of the moving mechanism generate heat, thermal atmosphere in this situation is exhausted from the cover, and is not exerted on the substrate. As the result, preferable film can be formed on the substrate.
Further, according to a third aspect of the invention, in the film forming unit of the present invention, the aforesaid support member has a discharge nozzle holding member for holding the discharge nozzle, the discharge nozzle is attachable and detachable to the aforesaid discharge nozzle holding member, and the aforesaid discharge nozzle holding member has a suction mechanism for sucking a part of the discharge nozzle.
As described above, since the holding member holds the discharge nozzle by means of the suction mechanism for sucking a part of the aforesaid discharge nozzle, the discharge nozzle does not fall off or is removed even if the discharge nozzle moves at a high speed. In addition, the discharge nozzle can be replaced. In place of the suction mechanism, a solenoid utilizing electromagnet can be used. In place of the suction mechanism, a pressing member swelled by inflow of air may be used. The holding member may be formed into a pocket shape, thereby housing the discharge nozzle in this pocket.
In order to attain the aforesaid second object, a film forming unit of the present invention includes a discharge nozzle provided to oppose the substrate held by the aforesaid substrate holding portion and discharging the coating solution onto the substrate held by the substrate holding portion, an X-direction drive section for moving the discharge nozzle in a direction X, a Y-direction drive section for the discharge nozzle for intermittently moving the discharge nozzle in a direction Y, and a Y-direction drive section for the substrate holding section for intermittently moving the aforesaid substrate holding section in the direction Y, and after the discharge nozzle is moved in the direction X and thereby the coating solution is applied onto a substrate top surface linearly, the discharge nozzle and the substrate holding portion are simultaneously moved intermittently in the opposite directions to each other in the direction Y to face the discharge nozzle to an area next to an area already coated, thus performing control to arrange the areas, which are coated in the direction X, in the direction Y in order.
Further, according to another aspect of the present invention, the film forming unit of the invention includes a substrate holding portion for holding the substrate, a first discharge nozzle and a second discharge nozzle provided to be separated from each other to oppose the substrate held by the substrate holding portion respectively and provided to oppose the substrate, an X-direction drive section for moving the first discharge nozzle and the second discharge nozzle in a direction X, and a Y-direction drive section for intermittently moving the first discharge nozzle and the second discharge nozzle, and the substrate holding portion relatively in a direction Y, and after the discharge nozzle is moved in the direction X and thereby the coating solution is applied onto a substrate top surface linearly, the first discharge nozzle and the second discharge nozzle are moved relatively in the direction Y to face the discharge nozzles to an area next to an area already coated, thus performing control to arrange; the areas, which are coated in the direction X, in the direction Y in order.
According to the above structure, since both the first discharge nozzle and the second discharge nozzle arrange the area which is coated in the direction X, in the direction Y, the processing can be performed in a shorter time compared with the processing performed with a single discharge nozzle.
In this aspect of the invention, the first discharge nozzle and the second discharge nozzle, and the substrate holding portion may be intermittently moved in the opposite directions to each other in the Y direction at the same time.
Further, the first discharge nozzle and the second discharge nozzle may be provided, for example, at a common base, and each discharge nozzle may move symmetrically in the opposite directions to each other. With this structure, impact occurring when the first and second discharge nozzle accelerate and decelerate is compensated each other and reduced.
Further in this case, the substrate holding portion includes a first substrate holding portion and a second substrate holding portion so that the first discharge nozzle discharges the coating solution to the substrate held by the first substrate holding portion and the second discharge nozzle discharges the coating solution to the substrate held by the second substrate holding portion, thereby further enhancing the processing efficiency.
Furthermore, according to another aspect, a film forming unit of the present invention includes a substrate holding portion for holding the substrate, a discharge nozzle provided to oppose the substrate held by the aforesaid substrate holding portion, for discharging the coating solution onto the substrate held by the substrate holding portion, a Y-direction drive section for intermittently moving the discharge nozzle relatively to the substrate holding portion in a direction Y; and a shock absorbing mobile body which moves symmetrically in an opposite direction relative to the discharge nozzle when the discharge nozzle is moved in the direction X, and after the discharge nozzle is moved in the direction X and thereby the coating solution is applied onto a substrate top surface linearly, the discharge nozzle is moved relatively in the direction Y to be faced to an area next to an area already coated, thus arranging the areas, which are coated in the direction X, in the direction Y in order.
In this configuration, since the shock absorbing mobile body moving symmetrically in the opposite direction to the discharge nozzle is provided, the impact caused by acceleration and deceleration of the discharge nozzle can be reduced as described above.
In the aforesaid invention, the X-direction drive section may include guide shaft members extending in the direction X for guiding the discharge nozzle, a nozzle holding body provided to enclose the guide shaft members via a space, and gas supply means for supplying pressurized gas into a portion between the nozzle holding body and the shaft members. According to this configuration, the discharge nozzle can be guided by the shaft members without bringing the shaft members and the nozzle holding body in contact with each other, whereby the friction and vibration caused by the movement of the discharge nozzle can be reduced.